6. Efficiency Improvement of Internal Combustion Engines Over Time

The demand for more efficient engines is increasing gradually and will continue to rise in the coming decades. In the present era, with the continuous rise in a global energy crisis and increasing ecological awareness, waste heat recovery became a common concern in various sectors of energy. The goal of this chapter is to address the role of waste heat recovery methods such as turbocharging, turbo-compounding, organic Rankine cycle, and thermoelectric generators, to enhance the thermal efficiency of the internal combustion (IC) engine over the past few decades. The maximum efficiency achieved in turbocharging is 44.1%, which is more than the conventional engines by 9.1–14.1%. The efficiency of turbo-compounding can be brought closer to 50%. The concept of compounded Rankine cycle increases the combined engine and waste heat recovery efficiency almost by 10%. The highest increment in the efficiency of the IC engine can be achieved with the thermoelectric generators which have tremendously increased the efficiency by almost 15–20%. This chapter provides some of the important basic information on IC engines and demonstrates some of the latest advanced technologies, such as engine downsizing, advance engine controls, variable valve timing, variable geometry engine design, advanced fuel injection, advanced compression ignition engines, advanced spark-ignition engines, alternative fuels that keep IC engines competitive due to their ability to improve the fuel economy and better performance of IC engines with near-zero emissions. Furthermore, the chapter presents opportunities, challenges, and technical barriers related to the future areas of IC engines.